Auditory brainstem implants

Auditory Brainstem Implants (ABI) are suitable for those with a profound sensorineural hearing loss, leading to near total loss of sound.

An auditory brainstem implant has two parts: an external part (the ‘processor’, worn on the ear) and the surgically implanted internal part. A microphone on the processor picks up the sound around it, and turns it from a sound wave into an electrical signal. The processor then transmits the sound signal to the internal part of the hearing implant. This consists of a receiver just below the skin, together with the implant array which is positioned within the brainstem.

This means that the implant is bypassing both the cochlea and the hearing nerve, taking a short cut to the brainstem. In this way the auditory brainstem implant aims to give a sense of sound when the hearing nerve is not working.

Image: Courtesy of Cochlear Europe.

Labelled cutaway diagram of the human ear showing the placement of different components of an auditory brainstem implant. The external processor with microphone on the outer ear, with the receiver and brainstem implant array inside the ear

Who can be considered for an ABI?

One main use of the auditory brainstem implant is for those with the condition Neurofibromatosis type 2 (NF2).  If you have NF2, you are likely to have a tumour on or near the hearing nerve. If this tumour is removed for medical reasons, the surgeons may well have to cut across the nerve of hearing. This brings about a complete breakdown of natural hearing in that ear. During the tumour removal surgery, the surgeon may consider placing an auditory brainstem implant as an alternative method of hearing.

Other uses of the auditory brainstem implant are for people who are born with no functioning nerve of hearing in either ear, or people who are deaf because of an unusually shaped cochlea. Sometimes meningitis leads to deafness but leaves the cochlea too damaged to take a cochlear implant. However, an auditory brainstem implant for one of these reasons is very rare, because the auditory brainstem implant requires neurosurgery.

What are the likely benefits of an ABI?

An ABI may provide a link to sounds when there would otherwise be no natural hearing at all. An auditory brainstem implant may help with lipreading.

Any drawbacks of an ABI?

An ABI involves complex neurosurgery to the brainstem. Your consultant would need to discuss all the risks with you.

The results of an auditory brainstem implant are extremely variable. It is a difficult task to position the auditory brainstem implant on the brainstem exactly to deliver sound. It is possible that there is no hearing sensation at all from the auditory brainstem implant.

In some cases the hearing sensation is within a narrow range so that sounds are not well differentiated. It takes time to adjust to the sound perceived through an auditory brainstem implant.

For further information on Neurofibromatosis Type 2 please contact:

Webpage reviewed: November 2022

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